The claim

“There really will be no second chances. If the UK breaks apart, it breaks apart forever.”
David Cameron, 10 September 2014

The background

David Cameron pleaded with Scots to vote against independence in an article in today’s Daily Mail.

The prime minister called the United Kingdom “a precious and special country” and said it would be destroyed forever if there is a yes vote on 18 September.

The sentiment has been echoed by many other pro-union voices. Earlier this week Alistair Darling said: “If we decided to leave there is no going back.” Nick Clegg said a yes voter was “a decision forever”.

But is that actually true?

The analysis

We contacted as many eminent historians and constitutional law experts as we could and asked them if there is any legal or constitutional reason why a vote for independence next week could not in fact be reversed in the future.

No one could think of one.

Professor Vernon Bogdanor from King’s College London told us: “The government of an independent Scotland could at any time seek to re-join the United Kingdom.

“But reversal of independence and re-union with the rest of Britain would be a difficult and cumbrous process.”

Professor Christine Bell from the University of Edinburgh law school said: “There is no legal, constitutional or international legal reason why union could not be put back together if both populations wanted  – only political ones.

“A clear vote either way is in practice not likely to be reversed within a generation (counting that at 15 years).  After that, all bets are on: according to the latest constitutional research – the average lifespan of a constitution globally is 19 years!”

Professor Aileen McHarg from the University of Strathclyde said: “Nothing’s impossible, just unlikely.

“Scotland and England (or rather England and Wales) were independent states when they entered into union in 1707, so it’s not beyond the bounds of possibility that they could decide to do so again at some point in the future.

“Or they might decide to go for some sort of confederal arrangement, short of full reunion.”

Our experts disagreed on how realistic it is to anticipate a second vote cancelling out the first. While most see a vote for reunion as only a distant possibility, others foresee a scenario where it could happen relatively quickly.

The Scottish National Party’s preferred deadline for a declaration of full independence following a yes vote is March 2016. But there are any number of reasons why the timetable might slip.

We still don’t know who exactly would represent the rest of the UK in the complex negotiations with the Scottish government that would have to come after a vote for independence. And the negotiations could hit all kinds of sticking points.

What if the negotiations are not completed by March 2016? Scotland elects a new parliament in May of that year. If the SNP loses power, would a non-nationalist Scottish government have a mandate to hold a second referendum cancelling out the first?

Prof Bogdanor said: “Suppose a Labour or Labour/Liberal Democrat government were returned.

“Might it not say – the terms for independence we are being offered are really not very good, we believe that independence is a mistake, and that Scots should have second thoughts in a second referendum?”

Of course this is all hypothetical. And we are in pretty uncharted territory, as there are few historical examples of countries separating voluntarily, only to choose to reunite later.

Germany was of course divided then reunified – but neither move was decided by a popular vote. Similarly, Hong Kong left China before re-joining it, but its citizens were not consulted on either occasion.

The verdict

The (unionist) politicians seem very sure that next week’s decision is irreversible. But that is not a view shared by any of the academics we canvassed today.

There doesn’t appear to be any cast-iron legal rule that says Scotland cannot rejoin the United Kingdom at some point after deciding to leave it.

Having said that, most of our experts think it politically very unlikely that Scots would be given the chance to pull a U-turn in the near future.

Equally, there does not appear to be any legal or constitutional reason why nationalists cannot seek another referendum in the future in the event of a narrow win for the no campaign.